Hi @jwn, sorry for the delay here, but I was working with Evan directly on this and thought we had sorted out the issues here. If you're still seeing any problems please me know.

Going over some of the questions here:SMTP tokens cannot be moved between portals, and the developer portal won't be able to use the Content tools UI, so you'd need to generate new tokens for the separate test smtp-testing portal.

API keys are specific to each portal. The Developer HAPIkey you'd see in the developer account would only be used to access ome of the settings for the Workflows or Timeline API for apps you create, so you'd need to get a separate API key for the test portal. We have instructions for getting the API key here:knowledge.hubspot.com